Two stage pump



STEFA TWO STAGE PUMP Sept 1965 Dec 6.

BY ATTORNEYS M H w m i N M. O J

3,208,389 TWO STAGE PU John P. Stefan, Birmingham, Mich, assignor to Ford Motor (iompany, Dearhorn, Mich, a corporation of Delaware Filed Dec. 6, 1962, Ser. No. 242,699 6 Claims. (Cl. 10398) This invention relates to a two stage pumping device and more particularly to a compound pump in which a first stage of the pump is driven continuously and a second stage of the pump is driven intermittently.

The rate of discharge of all fluid pumps is dependent upon the speed they are driven. In pumps of the positive displacement type the rate of discharge increases in direct proportion to the increased driving speed. Pumps of the centrifugal type have a rate of discharge that increases with the square of the driven speed.

In many applications it is necessary to drive a fluid pump from a prime mover that operates over a widely varying speed range. In some of these applications the variable rate of discharge of the pump caused by differences in the driving speed can be tolerated, however, in other instances the varying rate of discharge is not acceptable. In any event, when a pump is driven by a variable speed prime mover, a compromise in pump design in almost always required. This is particularly true with respect to centrifugal pumps where a small change in driving speed can produce a significant difference in the rate of pump discharge.

The cooling system water pump of an internal combustion engine is a typical example of an application where the use of a centrifugal pump driven by a variable speed prime mover requires a compromise in pump design. If the pump is designed to provide sutficient coolant flow for cooling at low engine speeds there may be too great a rate of flow at higher engine speeds. Alternatively, the characteristics of the engine may necessitate a greatly increased rate of flow at higher engine speeds without requiring a high magnitude flow at low engine speeds. The single stage pumps heretofore utilized have dictated design compromises and have not permitted an optimum rate of coolant flow at all engine speeds.

It is, therefore, the principal object of this invention to provide a pumping mechanism in which a first range of pump discharge is provided for a given driving speed range and in which a considerably different discharge rate is provided for another driving speed range.

A pump embodying this invention comprises first pumping means that is driven simultaneously with a rotating driving shaft. Second pumping means are provided that are driven intermittently by the driving shaft. A speed responsive clutch is interposed between the driving shaft and the second pumping means to cause a driving relationship during a first speed range and a nondriving relationship during a second speed range.

In one embodiment of the invention the second pumping means is disconnected from the driving shaft until the speed of the driving shaft exceeds a predetermined rate. When the predetermined speed is reached the second pumping means is drivingly coupled to the driving shaft to cause a significantly increased rate of discharge.

In other embodiments of the invention the second pumping means is drivingly connected to the drive shaft at lower drive shaft speeds. When the speed of the drive shaft exceeds a predetermined rate, the driving connection is disengaged to cause a significantly decreased rate of discharge.

Other objects and advantages of this invention will become more apparent as this description proceeds par- "ice ticularly when considered in connection with the accompanying drawings, wherein:

FIGURE 1 is a cross sectional view of a two stage centrifugal pumping device showing a first embodiment of the invention.

FIGURE 2 is a cross sectional view in part similar to FIGURE 1 showing another embodiment of the invention.

FIGURE 3 is a cross sectional view in part similar to FIGURES 1 and 2 showing a still further embodiment of the invention.

In the drawings similar parts in the various embodiments have been represented by the same reference numeral.

Referring now in detail to the embodiment of FIGURE 1, a coolant system pump of an internal combustion engine is indicated generally at 11. The pump 11 comprises a housing 12 that rotatably supports a drive shaft 13. The drive shaft 13 is driven from the engine crankshaft either directly or by means of pulleys and belts (not shown).

Formed within the housing 12 is a pumping cavity 14 that contains an inner impeller 15 having vanes 16 and an outer impeller 17 having vanes 18. The inner impeller 15 has a hub portion 19 that encircles the drive shaft 13 and is fixed for rotation therewith by a key 21. The outer impeller 17 has a hub portion 22 that extends in part into a cavity 23 formed in the hub portion 19 of the inner impeller 15. The hub portion 22 is rotatably supported upon the drive shaft 13 by an antifriction bushing 24. A seal 25 is interposed between the bushing 24 and hub portion 22 and the inner surface of the cavity 23. The impellers 15 and 17 are axially aligned on the drive shaft 13 to load the seal 25 by a snap ring 26.

The outer impeller 17 is adapted to be drivingly connected to the drive shaft 13 through the inner impeller 15 by the speed responsive clutch indicated generally at 27. The speed responsive clutch 27 comprises a plurality of substantially radially extending bores 28 formed in the inner impeller 15 in which ball detents 29 are received. A coil spring 30 contained within the bores 28 and compressed between the ball detents 29 and plugs 31 positioned in the outer end of the bores 28 urges the ball detents 29 toward the inner termination of the bores 28. A plurality of recesses 32 for reception of the ball detents 29 are formed in the part of the hub portion 22 that extends into the cavity 23 adjacent the inner termination of the bores 28.

At low engine speeds the speed responsive clutch 27 is engaged (FIGURE 1) and the inner and outer impellers 15 and 17 rotate as a unit with the drive shaft 13. Engine coolant is drawn through a coolant inlet 33 formed in the housing 12 and is circulated by the rotating vanes 16 and 18 of the impellers 15 and 17 into a collecting chamber 34 at the periphery of the cavity 14 for discharge into the engine cooling system. The vanes 16 and 18 are radially aligned to provide a smooth continuous flow path for the coolant.

As the engine speed increases, the centrifugal force acting upon the ball detents 29 increases until it reaches the point at which the centrifugal force exceeds the preload on the springs 30. When this occurs the ball dethe clutch 27. The drive shaft 13 and inner impeller tents 29 will move free of the recesses 32 disengaging 15 then rotate with respect to the outer impeller 17 which idles freely on the bushing 24. This produces an instantaneous decrease in the pumping capacity. The flow of coolant pumped is dependent solely upon the pump characteristics of the inner impeller 15 until the speed of the drive shaft 13 again falls below the predetermined speed at which the speed responsive clutch 27 is disengaged.

The speed at which the clutch 27 disengages may be varied by changing the weight of the ball detents 29, their radial location and by varying the preload of the coil springs 30. The rate of change in pumping capacity may be varied by changing the relative diameters of the inner and outer impellers and 17.

It is further noted that the recesses 32 formed in the hub portion 22 of the outer impeller 17 are circumferentially spaced in a manner to insure that the vanes 16 and 18 will always be aligned when the speed responsive clutch 27 is engaged. When so aligned, the vanes form a continuous pumping surface and act as a single unitary impeller.

Referring now to the embodiment of FIGURE 2, the coolant pump is indicated generally by the reference numeral 51. In this embodiment the outer impeller 17 is fixed for rotation with the drive shaft 13 by a key 52. The inner impeller 15 is rotatably supported on the drive shaft 13 by an anti-friction bushing 53. A speed responsive clutch, indicated generally at 54, comprises a plurality of generally radially extending bores 55 formed in the outer impeller 17. The bores terminate at their inner extremity adjacent the periphery of the inner impeller 15. Contained within the bores 55 are ball detents 56 that are urged by coil springs 57 into registry with recesses 58 formed in the periphery of the inner impeller 15.

As in the embodiment of FIGURE 1, the recesses 58 are circumferentially spaced in a manner that when the clutch 54 is engaged, the vanes 16 and 18 will be in registry to provide an uninterrupted flow path.

The operation of the embodiment of FIGURE 2 is similar to that of FIGURE 1. When the drive shaft 13 is rotated at low speeds, the coil springs 57 urge the ball detents 56 into registry with the recesses 58 causing the inner impeller 15 and outer impeller 17 to rotate as a unit. As the speed of the drive shaft 13 reaches a predetermined rate, the centrifugal force on the ball detents 56 exceeds the preload of the coil springs 57 and the ball detents 56 move free of registry with the recesses 58 to disengage the clutch 54. This permits an instantaneous decrease in the rate of pump output by permitting the outer impeller 17 to continue to rotate with the drive shaft 13 while disengaging the inner impeller 15 and permitting the latter to idle on the bushing 53.

At times it may be desirable to have a sudden increase in pump discharge upon reaching a predetermined speed. The embodiment shown in FIGURE 3 achieves this result. In FIGURE 3 the pump is indicated generally by the reference numeral 61 and comprises an inner impeller 15 that is fixed by a key 62 to the driving shaft 13. The outer impeller 17 is rotatably supported upon the driving shaft 13 by an antifriction bushing 63. A speed responsive clutch mechanism indicated generally at 64 is interposed between the inner and outer impellers 15 and 17.

The speed responsive clutch 64 comprises a plurality of generally radially extending bores 65 formed in the inner impeller. Reciprocally received within the bores 65 are a plurality of detents 66. Coil springs 67 are connected at one end to the detents 66 and are restrained at their other end by pins 68 that are secured to the inner impeller 15 adjacent the inner termination of the bores 65. A plurality of recesses 69 are formed in the inner periphery of the outer impeller 17 for the reception of the detents 66.

The coil springs 67, because of their tension, normally hold the detents 66 out of registry with recesses 69. At low engine speeds the drive shaft 13 rotates only the inner impeller 15 to cause a low rate of fluid discharge. As the speed of the drive shaft 13 exceeds the predetermined speed at which the centrifugal force on the detents 66 overcomes the tension in the coil spring 67, the speed responsive clutch 64 becomes engaged. The detents 66 then move into registry with the recesses 69 and cause the inner and outer impellers 15 and 17 to rotate as a unit. This causes an immediate and substantial increase in the rate of discharge of the pump 61.

As in the other described embodiments, the recesses 6 are circumferentially spaced so that the vanes 16 and 18 are aligned during simultaneous rotation of the inner and outer impellers 15 and 17 to provide continuous flow path through the pump.

It is to be understood that various other embodiments other than those described may be made without departting from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. A two stage centrifugal pumping device comprising a pump housing having a fluid inlet and a fluid outlet, a drive shaft rotatably supported by said pump housing, axially aligned inner and outer impellers contained within said housing, one of said impellers being affixed for rotation with said shaft and the other of said impellers being rotatable with respect to said one of said impellers, and speed responsive clutch means disposed between said impellers, said speed responsive clutch means disengaging and permitting freewheeling of one of the impellers at high speed of shaft rotation and engaging to fixedly lock the impellers together for simultaneous rotation at low speed of shaft rotation.

2. A two stage centrifugal pumping device comprising an inner impeller, an outer impeller, a rotatable shaft, one of said impellers being fixed for rotation with said shaft and the other of said impellers being rotatable with respect to said shaft, said one of said impellers being provided with a substantially radially extending bore terminating adjacent a portion of said other of said impellers, a detent reciprocally received in said bore and adapted to be moved axially therein by the centrifugal force exerted by the rotation of said one of said impellers, biassing means for resisting axial movement of said detent in said bore, and a recess adapted to receive said detent formed in the portion of said other of said impellers adjacent the termination of said bore.

3. A two stage centrifugal fluid pumping device comprising a rotatable shaft, an inner impeller fixed for rotation with said rotatable shaft, an outer impeller rotatable with respect to said shaft, said inner impeller being provided with a substantially radially extending bore terminating adjacent a portion of said outer impeller, a detent reciprocally received in said bore and adapted to be moved axially therein by the centrifugal force exerted by the rotation of said inner impeller, biassing means resisting centrifugal force induced axial movement of said detent means, and a recess formed in the portion of said outer impeller adjacent the termination of said bore and adapted to receive said detent.

4. A two stage centrifugal pumping device comprising a rotatable shaft, an inner impeller fixed for rotation with said rotatable shaft, an outer impeller having a hub portion rotatably supported by said shaft, said hub portion of said outer impeller extending axially into a cavity formed in said inner impeller, a substantially radially extending bore formed in said inner impeller terminating in said cavity adjacent the hub portion of said outer impeller, a detent reciprocally received in said bore and adapted to be moved axially therein by the centrifugal force exerted by the rotation of said inner impeller, and spring biassing means contained within said bore biassing said detent toward the hub portion of said outer impeller, and a recess formed in said hub portion for the reception of said detent.

5. A two stage centrifugal pumping device comprising a rotatable shaft, an outer impeller fixed for rotation with said rotatable shaft, an inner impeller rotatable with respect to said rotatable shaft, a substantially radially extending bore formed in said outer impeller terminating adjacent the periphery of said inner impeller, a detent reciprocally received in said bore and adapted to be moved axially therein by the centrifugal force exerted by the rotation of said outer impeller, spring biassing means contained within said bore urging said detent toward said inner impeller, a recess formed in the periphery of said inner impeller for the reception of said detent.

6. A two stage centrifugal pumping device comprising a rotatable shaft, an inner impeller supported upon said shaft, said inner impeller having a plurality of circumferentially spaced vanes formed on one of its surfaces, an outer impeller supported upon said shaft, said outer impeller having a surface with circumferentially spaced vanes formed thereon, the vanes of said impellers being axially aligned, one of said impellers being fixed for rotation With said shaft and the other of said impellers being rotatable With respect to said shaft, said one of said impellers being provided with a substantially radially extending bore terminating adjacent a portion of said other of said impellers, a detent reciprocally received in said bore and adapted to be moved axially therein by the centrifugal force exerted by the rotation of said one of said impellers, biassing means for resisting axial movement of said detent in said bore, and a plurality of recesses adapted to receive said detent formed in the portion of said other of said impellers adjacent the termination of said bore, said recesses being circumferentially spaced to cause circumferential alignment of the vanes of said inner and outer impellers when said detent is received in any one of said recesses.

References Cited by the Examiner UNITED STATES PATENTS 1,782,513 11/30 Roos 230-270 1,827,039 10/31 Ragan 230-270 2,203,843 6/40 Pierce 230-131 2,336,877 12/43 Matthews et al. 253-77 2,678,031 5/54 Spase et al. 230-271 2,819,703 1/58 Suttle 230-270 2,820,588 1/58 Penn et a1. 230-114 FOREIGN PATENTS 931,344 10/47 France. 1,033,790 4/53 France. 1,124,752 7/56 France.

22, 082 5/ 83 Germany.

17,607 1890 Great Britain.

KARL J. ALBRECHT, Primary Examiner.

JOSEPH H. BRANSON, JR., LAURENCE V. EFNER,

Examiners. 

1. A TWO STAGE CENTRIFUGAL PUMPING DEVICE COMPRISING A PUMP HOUSING HAVING A FLUID INLET AND A FLUID OUTLET, A DIRVE SHAFT ROTATABLY SUPPORTED BY SAID PUMP HOUSING, AXIALLY ALIGNED INNER AND OUTER IMPELLERS BEING AFFIXED FOR IN SAID HOUSING, ONE OF SAID IMPELLERS BEING AFFIXED FOR ROTATION WITH SAID SHAFT AND THE OTHER OF SAID IMPELLERS BEING ROTATABLE WITH RESPECT TO SAID ONE OF SAID IMPELLERS, AND SPEED RESPONSIVE CLUTCH MEANS DISPOSED BETWEEN SAID IMPELLERS, SAID SPEED RESPONSIVE CLUTCH MEANS DISENGAGING AND PERMITTING FREE WHEELING OF ONE OF THE IMPELLERS AT HIGH SPEED OF SHAFT ROTATION AND ENGAGING TO FIXEDLY LOCK THE IMPELLERS TOGETHER FOR SIMULTANEOUS ROTATION AT LOW SPEED OF SHAFT ROTATION. 